High-pressure steam turbine and method of utilizing high-pressure steam therein



1 1,632,907 June 21 27 F. LUSEL I HIGH PRESSURE STEAM TURBINE AND METHOD01" UTILIZING HIGH PRESSURE STEAM THEREIN Original Filed 2 Sheets-Sheet1 Aug. 13, 1924 ATTORN June 21. 1927-.

7 ;ru5/ avr arex/mA/fl 6950/75/77 (oases) F. LCSSEL HIGH PRESSURE STEAMTURBINE AND METHOD OF UTILIZING HIGH PRESSURE STEAM THEREIN 2Sheets-Sheet Original Filed Aug. 15, 1924 Q? L 0.25 I" I S tLJf//{Y/EOWOZVj/j INVENTOR 50/72 (5": BY P/M rd F ra ATTORNEY PatentedJune 21, 1927.

nuns!) STA FRANZ nosEL, or BRUNN, CZECHOSLOVAKIA.

HIGH-PRESSURE STEAM TURBINE AND METHOD or UTILIZING HIGH-PRESSURE s'rmmTHEREIN.

Continuation of application SeriaI No. 731,722, filed August 13, 1924,and in Denmark March 3, 1924.

This application filed May The invention-relates to high or, back pres-This is a continuation of my application Serial. No. 731,722, filedAugust 13, 1924:.

VVhileit has long been recognized that steam may be generatedmost'economically. at the higher pressures, prlor turbines have been illadapted to the use of very high pressures, because the increased lossesincident.

to the high pressure operation of these prior structures neutralize insubstantial part the economy which may be effected by thevhigh pressuregeneration.

The invention contemplates a turbine .capable of utilizing such highpressure steam at substantially turbines and resides in the applicationof certain novel principles of construction and operation to turbinestothat end. The invention also contemplates a turbine into,

which these principles may be economically and practically embodiedf Myinvention relates more particularly to a turbine of the character setforth in my Letters Patent #1, 494350, May 20, 1924, wherein theoperating steam velocities are .zept within the low velocity zonediscovered by me to be peculiarly efiicientas compared with the highervelocity zones of prior turbines. Experience has shown that turbines ofthis type when designed for very high pressures have not had as high anetiiciency as at lower pressures. I have discovered that this is notnecessarily due, as generally supposed, mainly to Wheel friction andventilation losses, but that thelosses incident to thrust compression inthe rotating blade canals, which are negligible at low pressures at anyrelative steam velocity practical for low pressure operation,disproportionately increase at high pressures and correspondingly highdensities and seriously reduce the working output. The thrust compression (and incident losses here dealt with) is better efficiencies thanprior 19, 1925. Serial No. 31,463.

that due to 'thealterationof direction of flow through the rotatingcanals and to the alteration of the canal sections, and is afunction ofthe density (or working pressure) and the velocity of'flow and increasestherewith at the higher pressures and densities. These losses includethe energy loss in the compression and expansion, the internal andhydraulic losses of the fluid flow, the enhanced leakage losses, andprobably others directly or indirectly due to the thrust in- ,7terference with the normal and regular flow and expansion of the highdensity steam. I have found, however, that such losses and impairment inefficiency may be substantially reduced by constructing the high pres-.sure portions of the turbine for operation at substantially lowerrelative steamvelocitiesthan would be practicable in the lower pressureparts of the turbine. While, however, relative steam velocities must berelatively lowered in the higher pressure zone of the turbine for goodefiiciency, there is a critical range in velocities below which one mustnot go in constructing the turbine, otherwise the gain in reduction ofthrust compression losses is offset by other considerations. It is notonly necessary, therefore,

that the comparatively low relative steam velocity, as set forth in theabove referred to Letters Patent. should exist throughout the turbinefor good efficiency, but taking into consideration the thrustcompression and losses incident thereto in the higher pressure zones andthat the multiplication of the stages in the very high pressure zonesdoes not materially or substantially add to the cost, wei ht and size ofthe turbine, it is essential or best performance in these very highpressure turbines here contemplated that they be constructed foroperation at relative steam velocities substantially lower than arefound necessary for the lower pressures. The velocity must be selectedand chosen for'each turbine part, and the latter accordingly constructedand proportioned, such. as to keep and malntain the thrust compressionwithin the permissible limits or zone representing best or maximumefficiency, and economy andpracticable embodiment of these princi lesmust also be taken into consideration. M invention, therefore, residesin a high 1 pressure turbine having its stationary and rotating canalsconstructed and proportioned in accordance with these principles and tothe ends that thethrust compression. losses do not exceed thepredetermined practicably permissible value in any stage or stage groupthroughout the highrpressure part of the turbine and that the elasticfluid velocities and thrust compressions throughout the turbine shallcome withln the limits or zone found by me to give satisfactory per:

formance notwithstanding the high pressure operation.

I have obtained data showingthe relation between the thrust compressionand relat ve velocity at various pressures within the high pressure zonehere under consideratlon, and

these data afford a ready guide means for properly proportioning'theturbine canals and parts to obtain the substantially thrustlessexpansion of the steam throughout the "high pressurezonc. may be soproportioned as to obtam a substantially constant and uniform thrustcom- If desired, the parts pression value throughout the various. stagesof the rotating turbine elements and within the critical rangediscovered by me to have the maximum efficiency, although in pract iceit will he usually sufficient to have the thrust. compression withinthis critical range without the necessity of a constant uniform thrustcompression throughout the high pressure zone. I thus secure a practicalhigh pressure turbine in which the losses due to compression thrusts arereduced to within practicable limits, even within the highest pressurestages, and which is therefore capable of operation at an eflici-encynot unduly impaired by the usual thrust losses and whose output is morenearly proportional to the large heat and pressure drops available atthe higher heat and pressure heads.

For a better understanding of my invention, reference may be had to theaccoinpan ing drawings forming a part of this app ication, of which:

Fig. 1 shows more or less diagrammatically a partial longitudinalsection through a disc wheel turbine with a pressure curve,

Fig. 2 illustrates a series of thrust compression curves,

Fig. 3 is a partial longitudinal sectional view through a disc wheelturbine embodying my invention, and

Fig. 4. shows an efficiency and economy curve in the high pressure zone.

Referring to Fig.1 the diaphragms of "a disc wheel turbine are indicatedby Le and the rotating wheels by La. The stationary guide nozzles areindicated by m and i increase byi passing through the rotating canals n.1e pressuretheoretically should have a. substantially constant value inim-,

pulse turbines or in certain'casesa decreasing value, if there 1s acertain reaction cle- Vgree, while passing through 'the rotating canalsn of the rotating'wheelsp The pressure curve P is shown for an impulseturbine. The dotted lines R connectin the horizontal portions of thecurve P. in icate thetheoretically constant value of the pressure whilepassing 'through the rotating chambers or canals n and the humps R inthe curve "above these dotted portions indicate theincreases in pressureAg) of the clasticfluid due to the compressive thrusts of the elasticfluidwhenits direction is altered in passing through acanal n or it ispassing through ana-ltered passage or reduced section. These compressivethrusts, resulting in the compression of theelastic fluidwithin therotating wheels and indicated by the irregularities R in the expansioncurve P, disturb the expansive working of the elastic fluid and impairthe efficiency of the turbine.

1 have foundby actual'tests that the losses due to these thrustcompressions, while negligible at the lower pressures and densities,become relatively ofincreasing importance at the higher pressures anddensities and for best turbine performance must be taken intoconsideration in constructing a turbine for these very high pressures.,I have referredparticularly to the thrust compression and incidentlosses occurring in the ro- 'tating canals because such losses are theprincipal thrust losses, though of course there is a slight thrustcompression loss in the stationary nozzles whichfis also substantiallyreduced by my invention.

In Fig. 2 is illustrated a series of thrust compression curves plottedbetween pressures and relative velocities, each corresponding to asubstantially constant thrust compression throughout the turbine andbased upon the data empirically determined. These curves showtheinfluence of steam pressure 2 (density) and relative steam velocity ron the thrust compression Ap.

Curve 1 shows the local increase of pressure Ag; of 0.1 atm. Within thecanals; curve 2, Ap:0.2 atm.; curve 3, A;I ::O.25 atm.; curve at apressure of 3 atmospheres of the working fluid; an increase of 0.2 aim.at T fitllL; of 0.3 atm. at 12 atm.; and there would be a Ap of 1 atm.at 86 attn. These curves that with an equal r increasing relative steamvelocity the thrust compressions increasing considerably in the highpressure stages of the turbine part. The losses due to thesecompressions disproportionately increase at the very high pressures andare unduly large in prior high pressure turbines, resulting in usefuloutputs which are not proportional to the larger heat (pressure) dropavailable at the higher pressure (heat) head.

' According to this invention the high pressure turbine or the highpressure part of a turbine is to be so constructed that the expansion inthe highest pressure zone occurs in a practically thrustless manner,that is, the relative velocities of the working fluid at these highpressures while permitted to vary from the high pressure part towardsthe low pressure part, are kept within such limits that the compressionthrusts he not surpass the upper practically permitted value throughoutthe whole high press zone of the turbine, and that the steam velocitiesare kept above the lower practicable limits. The critical range andapproximate limits in terms of efliciency, economy and actual thrustcompressions are generally indicated in Fig. 4 wherein the curve g isplotted between thrust compressions and etliciency (economy). This curveshows that theefiiciency of the turbine begins to decrease rapidly asthethrust compression goes above 0.35 atm. and approaches 0.4 atnr,

indicating a marked increase in the thrust compression losses at thesepoints, while at about 025 atm. the efliciency and economy appear as amaximum (point r). If steam velocities are chosen so as to give thrustcompressions below 0.25 atm. the efficiency and economy while notdecreasing rapidly at first, begin to show a marked drop in theneighborhood of 0.1 atm. (pointt) which indicates that the gain inreduction of thrust losses by lowering the velocity and thrustcompression to this extent is ofiiset byjin creased losses in otherdirections. Moreover, constructional problems and costs determinegenerally that the velocities shall not be lower than thosecorresponding to the thrust compressions approximating 0.1 atmosphere.The lower practicable limit therefore for the velocity in any high pressure stage is that corresponding to a thrust sho W compression ofapproximately 0.1 atm.while the upper limit of thrust compression'ls inthe neighborhood of 0x1 atm. Higher thrust compressions than the latterresult in sub stantial losses including the energy compression-expansionloss and internal hydraulic otthe expanding and working fluid that dueto the resultant damming up and retarding and interference with oropposition to the normal steam expansion, a perhaps slight increase inthe friction, windage and centrifugal losses, and the increasedpet'lpllfilfll leakage losses, aggravated by the very high steam densityand very small speeitic volume of the high pressure steam here underconsideration. The best and most iavorable range is'that in theneighborhood of a thrust compression of 0.25 atm; but departurestheretrom may be made in certain cases to meet the practicalrequirements, though generally the upper and lower limits 0.4 atm. and0.1 atm. respectively should not be disregarded, if highest efficiencyin each stage and best turbine economy are to be secured. T ie relativevelocities for the difterent high pressure zones of the turbine isobserved from the economy curve of Fig. hat the efiicieney decreasesmore rapas the thrustcoinpression is increased above the point '2" thanit does with a decrease oi" the compression below the point 1",indicating that the zone below 9* is generally more favorable toetliciency than the zone above.

)Vith the data and constant thrust compression curves of Fig. 2 as aguide, supplemented by the critical range and limits generally indicatedin Fig. 4, the guide nozzles and canals and turbine parts may beproportioned and constructed for each turbine stage so as to obtain thebest and most favorable performance. tained when the velocities andthrust compressions are kept within the limits above defined. Inaccordance with this invention there will be a general or averageincrease of the relative steam velocities from the high pressure endtoward the lower pres sure end, although for practical reasons, it maynot be desirable to construct the turbine tor a progressive increase invelocities from stage to stage, it being generally sufih cient thatdit't'erent successive zones or stage groups should be designed andconstructed with these limits in view. The thrust compression curvesthemselves may afford the grades for selecting the proper relative steamvelocity for each stage or stage group, or the torinulze correspondingthereto may be utilized for this purpose. For example, it the turbine isto be constructed for a thrust compression of 0.25 atm. (indicated asthe most favorable) throughout the high ould be chosen in accordancetherewith.

The latter is obpressure part of the turbine, then the formula may beutilized in the pressure zone between and 100 atmospheres, wherein g) isthe,

pressure in atmospheres absolute and 1 is the relative steam "elocity inmeters persecoud. Similarly there is a definite formula corresponding toeach ofthe other constant thrust compression curves. F or example, theformulafor np llxl-atm. is

in thelpressure zone between 30 and 100 atmospheres and the formula forAp: 0.1 atm..is i

7 These formulze and the constant thrust compreesion curves aredetern'iined from actual test data.

The thrust compress on curves of Fig. 2

3 indicate the increasing importance towards the high pressure end ofthe turbine of the proper and careful construction of the turbine partsWith reference to the fluid velocities. V For example, the constantthrust compression curves are observed to become more closely crowdedtogether Wlth the increase of and in each part of the turbine and theturbine construction is determined thereby.

I have lndicated more or less diagra-mmatlcally in Fig. 3 my inventionembodied, as for example, in a disc Wheel turbine, wherein the heightsof the orifices of the consecutive guide canals m are represented by a,b, c, d, c and the medium pitch or average diameters thereof by ,D, D,,D D D The products X 1v 2: 6 D41 y be considered as the'respectivemeasures of the exit sections for a full admission turbine, since thelength of a ring of orifices is proportional to the average diameter.The relative areas of the consecutive guide blade exit sections, ofwhich these products are the respective measures, determine the absolutevelocity in the respective stages, and in a practical turbine embodyingmy invention,

the ratio of such consecutive stationary guide nozzle exit sections havea predetermined relation to each other. The diameters D D etc. of thestages and the number of revolutions determine the peripheral speed ofthe rotating canals. The thrust compression curves corresponding to tthe practicall thrustless expansion, as above defined: throughout thehigh pressure part of the turbine, are based upon guidenozzleconstructions such that the ratio of a guide blade exit section to thenext. preceding exit, seet-ion is less than 1 (unity) but notsubstantially less than 0. 99 times the value of the ratio of the nextpreceding exit section wit, and for most favorableconditionsandoperation this value should be approximatel 0.997. These ratios may beexpressed as fol lows: e f a X 1 z. E-OBQ'YXgq, 9X 2 I (ix 3 X 3 6X 4 2O.997X

sections throughout of the proportions defined thereby, a substantiallyconstant thrustcompression of practically negligible or harmless valueexists throughout the turbine parts but as above indicated, a' constantthrust compression is notessential, though preferable. It will besuificient generally if V the different high pressure zones or stagegroups are constructed to approximate the relation expressed by theguide formulae given above, so longas the upper and lower limits offluid velocitiesand thrust compressions defined above are heeded in theconstruction.

My invention is particularly applicable to turbines of the disc Wheeltype, and by disc wheel'type I mean a turbine in which the impulsecharacteristics predominate over the reaction characteristics. Such aturbine when constructed according to the principles,

set forth above not only possesses'marked thermo-dynamic efliciency duetothe reduced elastic fluid velocities and thrust compres sion losses inthe high pressure part of the turbine, but by selecting and constructingthe turbine for the thrust compressions and fluid velocities of thefavorable order of magnit-ude coming within the etficiency and economyzone defined, namely above the minimum practical limits, a thoroughlyeconomical and practical construction is effected notwithstanding themultiplication of the stages with the attendant increase in length andweight. As above indicated the fluid velocities may be reduced and thestages multiplied in the high pressure part of the turbine withoutunduly increasing the bulk and weight of the turbine in view of the lowspecific volume of the high pressuresteam being dealt with.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A high pressure multistage steam turbine of the disc wheel lowvelocity type having its guide channels constructed and proportionedwith reference to each other and the steam pressure in each turbine partfor fluid velocities according to the formula where V is the relativesteam velocity in meters per second and p is the steam pressure inatmospheres.

2. A high pressure multistage steam turbine of the disc Wheel fulladmission type in which the channels through which the driving fluidflows are of a construction to give a decreasing relative steam velocityfrom the low pressure end to the high pressure end and in which therelative steam velocity in any high pressure stage is below that definedby the formula thereby obtaining substantially thrustless steamexpansion and working.

3. A high pressure multistage elastic fluid turbine of the disc wheeltype with admission pressures above 30 atmospheresin which the relativesteam velocity in any stage thereof does not exceed the valuecorresponding to the pressure-velocity formula wherein V is the relativesteam velocity in meters per second and 79 is the Steam pressure inatmospheres, thereby obtaining practically thrustless expansionthroughout the high pressure portion of the turbine.

4. A high pressure multistage elastic fluid turbine of the disc wheeltype with admission pressures above 30 atmospheres in which the relativevelocities through the high pressure stages thereof are determined by acurve plotted between pressure and velocity according to the formulawherein V is the relative steam velocity in meters per second and p isthe steam pressure in atmospheres whereby a pract1ca1ly thrustlessexpansion and working of the I tion to the next preceding bears apredetermined proportionate relation to the ratio of the next succeedingchannel section to the intermediatesection which is less than unity andgreater than 0.99.

6. A high pressure multistage steam turbine of the disc wheel type inwhich the ratio of an intermediate guide channel exit section to thenext preceding is substantially 0.997 times the ratio of the nextsucceeding section to the intermediate section.

7. A high pressure multistage elastic fluid turbine of the disc wheellow fluid velocity type having its steam flow canals of suchconstruction that the relative steam velocity in any stage thereof isless than that de lined by the pressure velocity formula 8. A highpressure multistage steam turbine of the disc wheel type having theguide openings of such relativesizos that a relative steam velocity ofless than IAO neters per second will result throughout the turbine, theratios of the successive guide open ings in the higher pressure stagesof the turbine closely approaching unity.

9. A multistage steam turbine of the disc wheel type having stagesdesigned for pressures exceeding 30 atmospheres, the nozzle openings ofsuch stages having size ratios predetermined with relation to thepressures for'which the stages are designed to give decreasing relativesteam velocities in the higher pressure stages generally correspondingto a change from about 90-100 meters per sec- 0nd in a thirty atmospherestage to about 6070 meters per second in a 100 atmosphere stage. I

10. A high pressure multistage elastic fluid turbine of the disc Wheellow fluid velocity type having its steam flow canals of suchconstruction that the relative steam velocity in any stage thereof isless than that deflned by the pressure velocity formula and more thanthat represented by the formula v 11. A high pressure multistage elasticfluid turbine of the disc wheel low fluid velocity and more than thatmula defined represented by the forthe'relative velocities at' thehigher pressure 10 end of the turbine'more closely approaching thesecondof saidformu'lw and those at the lower pressure end of the turbine moreclose- 1y approaching the first of said formulae.

In testimony whereof, I have signed my; I name to this specificatiomFRANZ LosEL.

